Systems and methods for delivering stimulation pulses using an implantable cardiac stimulation device

Abstract

Techniques are described for delivering inotropic electrical therapy to myocardial tissue using an implantable cardiac stimulation device such as a pacemaker. In one example, electrical stimulation is applied by a pacemaker to the heart of a patient while taking into account dynamic trans-cardiac impedance waveforms measured within the patient. In another example, a series of subthreshold inotropic stimulation pulses are delivered just prior to delivery of a suprathreshold depolarizing pulse that triggers systole. Additional subthreshold inotropic stimulation pulses can also be delivered following the suprathreshold pulse. Preferably, the magnitudes of the inotropic pulses are incrementally increased prior to systole then decremented thereafter, thereby gradually recruiting myocardium that has differing thresholds for depolarization. Both techniques seek to improve myocardial contractility of diseased tissue by improving calcium flux. Both techniques may additionally exploit the use of “multidimensional forced fusion”, described herein.

Description

FIELD OF THE INVENTION[0001]The invention generally relates to implantable cardiac stimulation systems for use in stimulating the heart and, in particular, to techniques for delivering inotropic stimulation, i.e. stimulation intended to affect the contractility of the heart.BACKGROUND OF THE INVENTION[0002]A variety of medical conditions affect the ability of heart muscle to properly contract in response to electrical stimulus—either intrinsic stimulus generated by the sinus node and conduction system of the heart or therapeutic pacing pulses delivered by a pacemaker or other implantable cardiac stimulation device. In particular, various cardiomyopathies of differing etiologies can affect myocardial contractility, and the temporal relationships of motion / contractility of various regions (dysynchrony). These effects can be secondary to a combination of primary disturbances in electrical conduction and pathologic myocardial tissue.[0003]Cardiomyopathy, i.e. “heart muscle disease”, per...

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Benefits of technology

[0014]Note that, depending upon the needs of the particular patient and the programming of the device, the inotropic stimulation thus delivered may be subthreshold, suprathreshold or a combination of the two. Furthermore, the inotropic stimulation may be selectively delivered during a refractory period or during non-refractory periods, again depending upon the patient, regional properties of any given innervated region and the programming of the device. Insofar as inotropic stimulation delivered during refractory periods is concerned, the invention provides a technique for automatically adjusting the parameters defining such non-excitory stimulation so as to potentially improve its inotropic effect where and when needed. Insofar as inotropic stimulation delivered outside refractory periods is concerned, such stimulation may include both subthreshold and suprathreshold components, delivered during systole and/or diastole. In particular, depending upon the needs of the patient, suprathreshold stimulation may be selectively delivered during systole along particular stimulation vectors while timed to trigger local depolarization that fuses with intrinsic and more global myocardial depolarization. That is, the suprathreshold ino

Problems solved by technology

Cardiomyopathy often results in heart failure as the pumping efficiency of the heart is diminished.

Patients with cardiomyopathy are often at risk for arrhythmia and/or sudden cardiac death (typically due to ventricular fibrillation).

In many cases, the affected side of the heart (i.e. the left side or the right side) will go into failure.

Heart failure that is sufficiently severe is referred to as congestive heart failure (CHF), which is a frequent cause of mortality in elderly patients.

Reduced contractility often results in a loss of cardiac output and also a lack of synchronous depolarization, i.e. a lack of coordination between the left and right cha

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